In recent years, research and development have been extensively conducted on light-emitting elements utilizing electroluminescence (EL). As a basic structure of these light-emitting elements, a layer containing a light-emitting substance is interposed between a pair of electrodes. Voltage is applied to this element to obtain light emission from the light-emitting substance.
The above light-emitting element is a self-luminous element; thus, a light-emitting device using the light-emitting element has advantages such as high visibility, no necessity of a backlight, and low power consumption. The light-emitting device using the light-emitting element also has advantages in that it can be manufactured to be thin and lightweight and has high response speed.
A light-emitting device including the above light-emitting element can have flexibility; therefore, the use of the light-emitting device for a flexible substrate has been proposed.
As a method for manufacturing a light-emitting device using a flexible substrate, a technology in which a separation layer is formed over a substrate, e.g., a glass substrate or a quartz substrate, a semiconductor element such as a thin film transistor is formed over the separation layer, and then, the semiconductor element is transferred to another substrate (e.g., a flexible substrate) has been developed (see Patent Document 1).